How Materials Work

In the real world, materials on the surface of objects have different properties that make the light that bounces off them react in specific ways. Glass, for example, lets light pass through it, metal shines by reflecting light, and wood absorbs light. Depending on the roughness of an object’s surface, the light will be reflected, and the reflection may be diffused (blurred) if the surface is rough. A surface that is hot enough can even emit light (such as tungsten or other hot metals).

In 3D, you can control the material parameters that make virtual light mimic the effects of light when it hits a surface in the real world. You can define a surface’s reflectivity or how much it shines, its color, its transparency, and its index of refraction. With different configurations for these values, you can imitate real-world materials inside the 3D world. Each one of these parameters of a material can be called a channel, and channels will be explained later in this chapter.